March 23-25, 2017: Impressive Day-to-Day Temperature Change, Including a Near-Record Quick Drop

March 23-25, 2017 Day-to-Day Change


Chicago temperature change from March 23-25, 2017			Rockford temperature change from March 23-25, 2017

Near-Record Quick Temperature Drop on March 24

March 24, 2017 brought a sharp late afternoon temperature fall to northeast Illinois and far northwest Indiana. This includes a 20° drop in five minutes near the lake front, and around 30° in just 30-60 minutes!

The meteorological feature responsible for this was a cold front, but one with strong lake enhancement. While this marine enhancement to a cold front can happen over the early spring chilled waters of the Great Lakes, to this extreme of magnitude is rare. These type of cold fronts are sometimes referred to as pneumonia fronts by meteorologists. These cold fronts tend to progress rapidly southward down the lake and shoreline areas due to the strong density and pressure differences between the air mass behind the front and ambient air mass ahead of it.


March 24 Observed Highs and Peak Gusts					March 24 Graphical NOWcast of Pneumonia Front

On Friday, March 24, strong southwest winds had steered in near-record to record warm air, with mid-afternoon highs in the lower 80s. Both Chicago and Rockford had only seen four other years reaching 80°+ this early in the season. Lake Michigan water temperatures on the other hand were in the upper 30s to lower 40s. As a cold front slowly moved down the lake during the daytime hours (peak heating over land), this thermal contrast set the stage for the surging cold front.

For Chicago (O'Hare), the temperature dropped 29° in one hour, dropping from 77° at 5:15 pm to 48° at 6:15 pm.
- The record dating back to 1872 for largest documented one hour temperature drop in Chicago was 30°, from 71° to 41° from 2 to 3 pm on March 26, 1908.
For Waukegan, IL (far northern Chicago metropolitan area), the temperature dropped 20° in just five minutes! It dropped from 79° at 3:05 pm to 59° at 3:10 pm. The one hour drop was 31° from 79° to 48°.

ORD Temperature Trace

Chicago O'Hare Temperatures

Chicago O'Hare Observations

UGN Temperature Trace

Waukegan Temperatures

Waukegan Observations

Other significant temperature drops in Chicago's history include:

A fall from 82° to 55° in just ten minutes on April 20, 1936. The temperature went on to fall to 32° by 4 a.m. on April 21.
Grant Park (not official) - a fall of 22° from 84° to 62° in 2 minutes and 30 seconds on May 9, 1963 due entirely to lake cooling.

NWS Chicago Science & Past Events Page